Arranged in a material testing machine performing material testing are a load mechanism giving a test load to a test piece and a plurality of detectors converting a physical quantity into an electric signal, examples of the detectors including a test force detector measuring a test force given to the test piece by the load mechanism and a displacement meter detecting displacement generated in the test piece. A physical quantity measuring system for material testing is configured by the detectors being connected to a testing machine controller controlling the entire material testing machine via an amplifier (see Patent Document 1).
In the related art, sensor amplifiers should be individually prepared, in view of the difference between the physical quantity measurement methods of the detectors, on a control device side for each detector to be connected to the control device of the testing machine. In this regard, an amplifier device for a displacement meter to which both a strain gauge type displacement meter and a differential transformer type displacement meter can be connected has been proposed in Patent Document 2 as a displacement detector detecting displacement generated in a test piece.
This type of detector is appropriately used through replacement with respect to a material testing machine main body depending on the types of material testing, and thus a measuring circuit constituting a physical quantity measuring system should be calibrated when the detector is installed in the testing machine main body or from time to time as necessary. In the case of load cells, calibration target value creation and so on are performed, by a load cell supplier or a supplier of apparatuses including load cells, by methods such as a method for inputting a rated capacity equivalent to a load cell and a method for actually giving a known load to a load cell. A load cell user performs work based on calibration information provided by the supplier in order to adjust the gain of a load cell-connected control device side amplifier and confirm the accuracy of test force display at a time when the known load is given.
The electrical measuring circuit calibration required for the user side operation is cumbersome for some users. Proposed in this regard is a control device in which a shunt resistance and a reference bridge circuit for amplifier calibration are provided at a part where a strain gauge type detector is connected so that calibration of an amplifier receiving input from the strain gauge type detector is automated (see Patent Document 3). Also proposed is a material testing machine with which amplifier gain adjustment can be automatically performed by a cable unit being provided with calibration impedance in a case where a differential transformer or a capacitive sensor is used for test piece displacement measurement (see Patent Document 4).